It is a general method of photocopying with an electrophotographic printer that a peripheral surface of a photosensitive drum is uniformly charged, the peripheral surface is exposed by the copied image of a subject so as to form an electrostatic latent image on the peripheral surface, toner is attached to the electrostatic latent image so as to form a toner image, and the toner image is copied on a sheet of paper and the like.
In such an electrophotographic printer, toner remains on the peripheral surface of a photosensitive drum after the toner image is copied and is generally removed by scraping with a cleaning blade 1 having a holding plate 2 as shown in FIG. 1.
As an elastic body employed for the cleaning blade 1, urethane rubber is prevalently used for its superior dynamical properties such as abrasion resistance. The cleaning blade 1 made of urethane rubber is produced, for example, by a prepolymer method comprising steps of providing a mold having a cavity for forming the cleaning blade, filling the cavity of the mold with a liquid composition containing prepolymer wherein polyisocyanate and polyol are partially polymerized (hereinafter referred to `urethane-rubber-forming prepolymer`), a curing agent and a catalyst, curing the composition and unmolding thus obtained cured matter.
However, it takes time in the above method to fill the cavity of the mold with a liquid composition and cure thereof, resulting in bad product efficiency. Even if the amount of a catalyst in the liquid composition is increased for shortening an unmolding time with intention to improve product efficiency, the liquid composition cannot spread uniformly through the mold because a curing reaction of the liquid composition rapidly progresses so that the viscosity thereof increases as the catalyst increases in amount, resulting in increase in the number of defects due to insufficient fluidity in case that triethylenediamine (TEDA), dimethylimidazole (DMIZ) or the like, prevalently used heretofore, is adopted as a catalyst. Further, since the liquid composition containing urethane residue cured in a mixing chamber of a casting machine is cast into the mold, cleaning properties of thus obtained product may be deteriorated. For this reason, it is a current situation that product efficiency can not be improved by increasing the amount of the catalyst. In addition, there is another problem that a large-sized molding can not be obtained because of low fluidity.